Fix for missing babel dependencies in with-rebass example (#16839)

Pull request for (Issue: Fix or remove the with-rebass example #16828). Just added some missing dependencies to the package.json of the example

Fixes #16839 

examples/with-rebass/package.json

@@ -7,6 +7,8 @@
   },
   "dependencies": {
     "babel-plugin-styled-components": "^1.1.7",
+    "babel-plugin-transform-object-assign": "^6.22.0",
+    "babel-plugin-transform-object-set-prototype-of-to-assign": "^6.22.0",
     "next": "latest",
     "react": "^16.7.0",
     "react-dom": "^16.7.0",